CN111527365A

CN111527365A - Container for recovering heat energy of waste water

Info

Publication number: CN111527365A
Application number: CN201880078632.6A
Authority: CN
Inventors: 约尼·海尔波莱宁; 阿尔尼·泰尔沃宁
Original assignee: Icopal
Current assignee: Icopal
Priority date: 2017-11-06
Filing date: 2018-11-06
Publication date: 2020-08-11
Also published as: KR20200084024A; EP3707453A1; EP3707453A4; CA3084627A1; JP2021501869A; WO2019086766A1; FI20175983A1; US20210199389A1; FI127909B

Abstract

The invention relates to a container (1) for recovering thermal energy from waste water. The container (1) comprises: a housing (10); and a continuous spiral pipe (2) for conveying the waste water through the container in a vertical direction. A first heat transfer space for transferring heat to the liquid is arranged between the outer shell of the spiral tube (2) and the shell (10) of the container (1), and a second heat transfer space is arranged inside the spiral tube (2). The shell (10) is provided with at least one openable inspection hatch (6) which is fastened with a manifold (7) and a shell-and-tube heat exchanger (3) having its inlet and outlet ends coupled to the manifold (7). The spiral tube (2) is composed of acid-resistant or stainless steel and its inner surface is adapted to have a higher chromium content than the rest of the spiral tube wall.

Description

Container for recovering heat energy of waste water

The present invention relates to a container for recovering thermal energy of waste water according to the preamble of claim 1.

In view of the recovery of thermal energy from municipal, in particular residential, waste water, there are known prior art recovery systems which comprise a shell-and-tube heat exchanger consisting of a tube side (primary side) and a shell side (secondary side) surrounding the former, the shell side carrying a heat transfer fluid. The tube side of shell-and-tube exchangers in some shell-and-tube heat exchanger models employ a spiral design for ensuring a good heat transfer area and thus heat transfer coefficient. However, these shell-and-tube heat exchangers with coil sides involve several problems if they are intended for the recovery of heat energy from dirty domestic waste water (so-called black water) and polluted municipal waste water.

Generally, such a waste water thermal energy recovery system (in which thermal energy of waste water is recovered into a heat transfer fluid by a shell-and-tube heat exchanger of the above-described type) is limited to recovering only thermal energy contained in one type of waste water, i.e., thermal energy mainly present in residential grey water, and on the other hand, the recovered thermal energy has been most commonly used only for heating domestic hot water.

Currently, there is no commercially available heat exchanger assembly that enables a single shell and tube heat exchanger with a preferred coil side (coil) to be used for contaminated municipal or domestic wastewater, especially black water, for the purpose of recovering thermal energy so that the heating or cooling energy of the wastewater can also be conducted to an optional non-pressurized or pressurized heat transfer fluid flowing in the shell side of such shell and tube heat exchangers.

This is due firstly to the fact that: energy recovery from dirty black water flowing inside the coils of a shell and tube heat exchanger, for example, can cause problems due to plugging of the heat exchanger tubes. If an effort is made to prevent coil clogging by replacing the coils on the tube side of the shell and tube heat exchanger with straight tubes, this will on the other hand result in a significant deterioration of the heat transfer coefficient of the shell and tube heat exchanger as the heat transfer area decreases and the residence time in the heat exchanger becomes shorter.

Therefore, the primary prevention of shell and tube heat exchanger contamination and the convenience of maintaining a contaminated shell and tube heat exchanger are among the most important aspects of utilizing a shell and tube heat exchanger equipped with a spiral piping system to treat dirty waste water, especially black water, and to attempt to supply the shell side with various heat transfer fluids as well. The prior art fails to provide a satisfactory solution to this particular problem.

Furthermore, if the tube side of such a shell-and-tube heat exchanger containing spiral tubes is to be supplied with waste water that may contain large amounts of various chemicals (i.e., waste water from indoor swimming pools), this will tend to cause corrosion problems that will significantly reduce the useful life of the tube side of the heat exchanger due to water-borne chemicals, such as chlorine.

On the other hand, if the various heat transfer fluids to be supplied into the shell side are to be expanded (the heating or cooling effect of the wastewater flowing in the tube side of the shell and tube heat exchanger may be transferred into the heat transfer fluid), problems may arise in calibrating the dimensions of the tube and shell sides of the shell and tube heat exchanger of the heat exchanger assembly. The reason for this is that when the energy recovery system is installed in an apartment building, in particular in the tube side of such shell-and-tube heat exchangers, it must be dimensioned to be able to withstand high pressures and/or pressure fluctuations.

This sizing problem can be at least partially solved by replacing the shell and tube heat exchanger with a spiral heat exchanger, wherein the heat transfer fluid is transported in its designated spiral next to the spiral waste. However, in this case, the overall heat transfer coefficient is significantly reduced compared to the use of a shell and tube heat exchanger in which the shell-side heat transfer fluid will directly surround the coils in which the wastewater flows.

The problems caused by pressurized wastewater can be addressed by sizing the tube and shell sides of a shell and tube heat exchanger based on the maximum minimum pressure that the tube side of the heat exchanger is designed to withstand. However, this may result in an excessively thick wall structure (in particular on the shell side of the shell-and-tube heat exchanger) and thus a reduced heat transfer coefficient.

Another problem with heat exchanger assemblies equipped with shell-and-tube heat exchangers and designed for the recovery of municipal and residential wastewater energy is generally the fact that the flow of wastewater into the recovery system and thus into the primary side of the shell-and-tube heat exchanger can be quite pulsatile. Therefore, in heat exchanger assemblies for recovering waste water energy, it has been necessary to accompany the heat exchanger with technically complicated flow and pumping devices in an effort to equalize the waste water flow in the primary side of the heat exchanger, especially in winter.

The container for recovering thermal energy of wastewater of the present invention is directed to solving the aforementioned problems occurring in the prior art.

It is therefore a primary object of the present invention to provide a vessel comprised of a shell and tube heat exchanger for recovering waste water thermal energy from domestic black water and dirty municipal water flowing on the tube side of the shell and tube heat exchanger comprised of spiral tubes into the heat transfer fluid surrounding the spiral tubes to the shell side of the shell and tube heat exchanger.

The aforementioned main object is achieved by constructing the vessel with sufficient elements for preventing contamination of the shell and tube heat exchanger beforehand and for cleaning the contaminated shell and tube heat exchanger.

Another object of the invention is to achieve as light a construction as possible on the tube side as well as on the shell side of the heat exchanger without making compromises that would jeopardize the overall pressure resistance of the heat exchanger.

A further object is to provide a shell and tube heat exchanger in which the thermal energy of the waste water flowing in the spiral tube can be recovered to the domestic water flowing inside the container without the domestic water and the waste water being able to mix with each other, because the waste water is constituted by so-called black water.

The invention further aims to make the tube side and the shell side of a shell-and-tube heat exchanger as simple as possible in construction. A particular object is to maintain the structure of the heat exchanger such that it does not comprise electric flow and pumping means dedicated to regulating the flow on the tube side of the heat exchanger.

The second starting point for the design is the ability to: in a vessel consisting of a shell-and-tube heat exchanger, the heating or cooling energy of the waste water flowing inside the spiral tube can be transferred to a possibly pressurized heat transfer fluid flowing on the shell side of the heat exchanger. The heat transfer fluid should be selected from a variety of heat transfer fluids that can be heated or cooled, such as primary side geothermal heat transfer fluids and ventilation heat transfer fluids.

In the present disclosure, the shell side (i.e., the secondary side) of the shell-and-tube heat exchanger refers to a first heat transfer space defined between the vessel shell and the shell of the spiral tube, and in which the heat transfer fluid flows. The energy of the waste water flowing in the spiral tubes present on the tube side or primary side of the shell-and-tube heat exchanger is recovered into the heat transfer fluid flowing on the shell side.

The recovery of thermal energy of the waste water refers in this context to the recovery of heating energy and cooling energy of the waste water, depending on whether the temperature of the waste water flowing on the tube side of the heat exchanger is higher or lower than the temperature of the heat transfer fluid on the shell side.

In the present disclosure, wastewater refers to a disposable water-based liquid that has been used for municipal or residential services. The waste water to be treated in shell-and-tube heat exchangers contains in particular black water.

It is the container according to claim 1 that achieves the aforementioned objects.

More specifically, the invention relates to a container for recovering the thermal energy of waste water according to claim 1. The container comprises: a housing outwardly defining a container; a continuous spiral pipe for transporting wastewater through the vessel in a vertical direction. The helical pipe communicates with an external vessel waste water inlet conduit via an inlet connection associated with the vessel shell and with an external vessel waste water outlet conduit via an outlet connection associated with the vessel shell. The vessel further comprising a first heat transfer space surrounding the spiral tube and defined by an outer shell of the spiral tube and by the shell of the vessel, and communicating with a heat transfer fluid inlet conduit via at least one heat transfer fluid inlet connection associated with the shell of the vessel and communicating with a heat transfer fluid outlet conduit via at least one heat transfer fluid outlet connection associated with the shell of the vessel; and a second heat transfer space left inside the spiral tube and defined by a shell of the spiral tube, whereby at least a portion of the vessel is provided as a pressure vessel. In the present invention

-the vessel having its shell provided with at least one, preferably two openable inspection hatches, at least one inspection hatch securing a manifold and a shell and tube heat exchanger, preferably a spiral shell and tube heat exchanger, having its inlet and outlet ends coupled to the manifold, the manifold being further provided with means for opening and closing a fluid connection with the shell and tube heat exchanger,

-said waste water pipe, as regards its material, consists of acid-resistant or stainless steel and has its inner surface treated so that, by said treatment, said spiral pipe at least has its inner surface adapted to have a higher average chromium content than the average chromium content of the rest of the spiral pipe wall.

Preferably, the surface treatment is carried out by electropolishing and is preferably carried out with a surface roughness below Ra 120.

Preferably, the spiral pipe also has its outer surface treated in the same way as the inner surface, i.e. the spiral pipe has its outer surface adapted to have an average chromium content higher than the average chromium content of the rest of the spiral pipe wall (excluding the inner surface). Thus, the inner surface of the spiral pipe, and often also the outer surface of the spiral pipe, is made of a steel material having a chromium content exceeding the core portion of the wall of the spiral pipe. In fact, it can be said that the chromium content becomes lower as going from the inner surface of the outer wall of the spiral pipe toward the core portion of the outer wall of the spiral pipe.

The invention is based firstly on the completion of at least one inner surface of the spiral pipe with a low surface roughness and, in addition, the inner surface of the spiral pipe is adapted to be electropolished or the like to have a higher average chromium content than the other parts of the spiral pipe wall (core part). Whereby the inner surface of the spiral pipe is already able to withstand corrosive sewage and, in addition, the pipe wall is already able to repel dirt, i.e. is already able to be self-cleaning. Third, in the present invention, the shell of the container is still provided with one or two openable inspection hatches.

In another aspect, the invention is based on the integral fitting of at least one inspection hatch, already coupled with at least one micro-auger (usually several micro-augers) for conveying, for example, domestic water or liquids for building cooling. A significant benefit is thereby obtained, since the inspection hatch and the manifold integrally coupled thereto and the micro-screw significantly facilitate and increase the reliability of the maintenance, since the manifold-inspection hatch-micro-screw combination constitutes a single compact entity.

Here, the blending between the domestic water remaining in the pipes inside the spiral pipe and the black water flowing in the spiral pipe is further prevented by the domestic water and the waste water which run completely separately from each other in their own pipes and between which there is always a flow of heat transfer fluid in the empty fluid space of the container.

The manifold-inspection hatch-micro-helix assembly is preferably validated and pressure tested prior to mounting the assembly on the vessel.

The vessel is preferably designed as a shell-and-tube heat exchanger, whereby the spiral tube defining the tube side and the vessel shell defining the shell side are designed as separate pressure vessels, the dimensions of which are calibrated with different standards. Since the waste water to be supplied to the tube side is often at a much higher pressure than the heat transfer fluid flowing on the shell side, it is thereby possible to ensure a sufficient pressure resistance on the tube side of the shell-and-tube heat exchanger without having to unnecessarily increase the wall thickness on the shell side.

A third important aspect of the present invention relates to the heat transfer space defined inside the spiral tube; in shell and tube heat exchangers, which are intended to treat dirty residential and municipal water (such as black water), the heat transfer space remaining inside the spiral tubes is equipped with at least one tube heat exchanger, preferably a spiral tube heat exchanger. The tubular heat exchanger has its inlet and outlet ends connected to a manifold, and the manifold is integrated with an inspection hatch present in the upper part of the vessel, and the same or different heat transfer fluids can be brought into the manifold from two different directions outside the vessel. Thereby providing the ability to heat/cool the heat transfer fluid flowing in the shell section of the shell and tube heat exchanger, for example with a separate heat exchanger that can be supplied with cooled condensed liquid from a building or liquid heated by solar radiation energy.

In a preferred embodiment of the invention, the container is provided with its housing and/or cover with one or more flange connections for a heat exchanger in order to transfer heat into or out of a heat transfer fluid present in the heat transfer space. One or more heat exchangers, such as a building's chilled condensate liquid or solar radiation energy collector, may extend into the heat transfer fluid flowing in the heat transfer space of the vessel through the flange connections.

In a preferred embodiment of the invention, the spiral tube has a continuous interior in view of providing an unobstructed passage for the liquid in said spiral tube. Since the liquid or gas travels unimpeded inside the spiral tube, there is no need to equip the vessel with electrical regulating elements or valves that control the passage of the liquid or fluid, and the vessel can be made very simple in construction on the tube side.

In a preferred embodiment of the invention, the helical tube has a helix angle of 0 to 10 degrees per helix.

Here, the helix angle of the helix refers to the angle of incidence of the centre line of the individual helix of the waste pipe (i.e. the upwardly directed helix of the helix tube) with respect to the horizontal plane of the helix tube, which is perpendicular to the longitudinal centre line of the helix tube.

In another preferred embodiment of the invention, the ratio of the heat transfer area of the spiral tube to the height of the vertical space defined by the spiral of the spiral tube may be varied.

The height of the vertical space defined by the spirals refers to the maximum distance between the highest spiral and the lowest spiral of the spiral pipe. On the other hand, the heat transfer area of the spiral pipe refers to the total surface area of the spiral pipe.

In yet another preferred embodiment of the present invention, the rate of heat transfer delivered by the spiral tube may be adjusted by the number of horizontal angles and the size of the angles present in the spiral of the spiral tube.

The horizontal angle of a helix or thread refers to the curvature or angle of the helix, wherein the radius of the helix as measured from the pipe centerline existing at the angle is different from the average radius of the same helix, or from the average radius of the helix as measured from the longitudinal (i.e., perpendicular) centerline of the helical pipe.

In another preferred embodiment of the invention, the heat transfer coefficient is adjustable by the helix radius of the helix tube relative to the vertical centerline of the helix tube.

The closest prior art to the present invention has been proposed in patent document DE 102010006882, which however does not describe a manifold equipped with an inspection hatch nor does it increase the average chromium content of the inner surface of the spiral pipe above that of the rest of the spiral pipe wall.

The invention and the benefits derived therefrom will now be described in more detail with reference to the accompanying drawings.

Figure 1 shows a vertical cross-sectional view of a vessel suitable for recovering thermal energy from waste water.

Fig. 2 and 3 show the container of fig. 1 from a slightly different perspective from the outside.

Fig. 4 shows the tubular heat exchanger 3 connected to the manifold 7 and coupled to the inspection hatch. The manifolded heat exchanger-inspection hatch assembly is also visible in fig. 1.

Fig. 5 shows a heat exchanger 81 which can be connected to the flange 8 visible in fig. 3 at the lower part of the shell of the tube heat exchanger 3 and which is here a spiral solar heat exchanger. The inlet and

outlet connections

82a, 82b of the solar heat exchanger 81 are connected by means of flanged joints to the lower part of the shell of the tubular heat exchanger 3 or to the heat transfer space 11 which is inside the tubular heat exchanger 3 and thus inside 11 these micro-spirals 3.

Fig. 6 shows a cross-section of the spiral pipe viewed directly from above.

Fig. 1 to 3 depict a first embodiment of the container 1 of the invention, which relates to a container suitable for recovering energy from residential and municipal wastewater.

Fig. 1 is a longitudinal sectional view showing a vessel 1 according to a first embodiment of the present invention, which is used as a shell-and-tube heat exchanger, particularly for recovering thermal energy from black water. Fig. 2 and 3 illustrate how the waste water and the heat transfer liquid are supplied into or withdrawn from the container.

As seen from the longitudinal sectional view of the vessel 1 shown in fig. 1, the vessel serving as a shell-and-tube heat exchanger has: a housing 10; and a continuous spiral pipe 2 for vertically conveying the wastewater through the container of the container 1. Typically, the black water travels through the container in a top-down direction under the force of gravity. The vessel is equipped with a holder 12.

The spiral tube 2 constitutes the tube portion of the heat exchanger and is connected to the heat exchanger via an inlet connection 2 associated with the vessel shell (see fig. 3); 21 communicate with a waste water inlet conduit outside the vessel and via an outlet connection 2 associated with the vessel shell (see figure 2); 22 are in communication with a waste water outlet conduit outside the vessel.

The coil 2 has its shell, i.e. the outer wall of the coil, directly surrounded by a first heat transfer space 4, which at the same time constitutes the shell part of the shell and tube heat exchanger. The first heat transfer space 4 is defined by the outer wall of the spiral tube 2 and by the outer shell (double shell) of the container 1. The first heat transfer space 4 is via at least one heat transfer fluid inlet connection 4 associated with the shell 10 of the container 1; 41 are in communication with a heat transfer fluid inlet conduit (not shown in the figures) and are connected to the container 1 via at least one heat transfer fluid outlet connection 4 associated with the shell 10 of the container 1; 42 communicate with a heat transfer fluid outlet conduit (not shown). Inside the spiral tube 2, a second heat transfer space 5 is left, which is thus located by the spiral 2 of the spiral tube 2; 2¹…2⁸In a defined vertical space. The container 1 is provided as a pressure vessel.

The construction of the shell 10 of the vessel 1 and the manifold 7 connected to the inspection hatch 6 (manhole) at the upper part of the vessel can be seen in more detail in fig. 2 and 3. As can be seen in fig. 2 and 3, the upper part of the shell 10 of the vessel 1 is provided with an openable inspection hatch 6 which is fastened with bolts 16 to a collar surrounding the upper part of the vessel.

A manifold 7 is integrated or firmly fixed on top of the inspection hatch 6 and is coupled with the shell and tube heat exchanger, as is not yet depicted in fig. 4. The manifold 7 comprises a first valve system or the like, by means of which the inlet paths for domestic water or heat transfer fluid from two different directions outside the container to the manifold 7 can be opened. The manifold 7 is further provided with means, such as a second valve system, for opening and closing a fluid connection from said manifold 7 to the spiral shell and tube heat exchanger 3 located in the second heat transfer space 5 of the vessel 1. The shell and tube heat exchanger has its inlet and outlet ends 31, 32 connected to the manifold 7. The shell and tube heat exchanger-manifold-inspection hatch assembly thus constitutes a detachable entity in itself, facilitating vessel maintenance. Inside the spiral heat exchanger an additional heat transfer space 11 is left, into which a separate spiral heat exchanger 81 can be introduced, wherein a heat transfer fluid is circulated, which is in communication with the recovery of solar radiant energy or with the condensate circulation of the building cooling system. It can be seen from fig. 3 how the flow V1 of the heat transfer fluid, such as water, reaches the manifold 7 and further to the interior of the container. The heat transfer fluid passes through the spiral shell and tube heat exchanger present inside the spiral tube 2 and at the same time delivers its thermal energy into the heat transfer space 5. Thereafter, a heated or cooled liquid stream, such as water stream V2, is discharged from the manifold 7 of the shell and tube heat exchanger 3 out of the vessel 1.

It can also be seen from fig. 3 how the first heat transfer space 4 (i.e. the shell part of the heat exchanger) is connected via a heat transfer fluid inlet connection 4; 41 is in communication with the heat transfer fluid inlet conduit and how via the heat transfer fluid outlet connection 4; 42 communicate with the vessel outer heat transfer fluid outlet conduit.

On the other hand, the wastewater stream is passed through an inlet connection 2 inside the container (see fig. 1); 21 to the upper part of the container. Inside the container, it moves downwards under the effect of gravity along the spiral tube 2 and at the same time delivers thermal energy to the heat transfer fluid present in the shell portion 4. Thereafter, the waste is passed through the waste water outlet connection 2; 22 are discharged from the container.

The material thickness of the wall of the spiral pipe 2 visible in fig. 1 is chosen such that the spiral pipe 2 has a maximum pressure resistance level of 10 to 16 bar, relative to the average cross-sectional diameter of the spiral pipe. The material thickness of the shell 10 of the container 1 is in turn selected such that the container has a maximum pressure resistance level of 4 to 10 bar with respect to the inner diameter of the container. The spiral pipe in the pipe section of the vessel 1 thus has a maximum pressure resistance level which is slightly higher than the highest possible pressure resistance level of the pipe section of the vessel.

On the other hand, the material thickness of the wall of the spiral pipe 3 visible in fig. 1 is selected such that the spiral pipe 3 has a maximum pressure resistance level of 10 to 16 bar with respect to the average cross-sectional diameter of the spiral pipe. Inside the helical coil 3 there can be conveyed domestic water which is heated by means of a heat transfer fluid flowing in the empty interior of the container 1, i.e. in the first heat transfer space 4. For its part extending inside the vessel 1, the helical coil 3 is entirely located in the second heat transfer space 5 and is surrounded from all directions by said heat transfer fluid flowing/existing inside the empty interior of the vessel 1. Therefore, the domestic water running in the spiral coil does not come into contact with the spiral tube 2 in which dirty black water flows at any point.

As regards its material, the spiral tube 2 intended for waste water and visible in fig. 1 is made of acid-resistant or stainless steel and has its inner surface treated, preferably by electrolytic polishing, to a low surface roughness, for example a surface roughness below Ra 120. In addition, the treatment of the inner surface of the spiral tube 2 is selected such that by said treatment the inner surface of the spiral tube 2 has an average chromium content adapted to be higher than the average chromium content of the other wall portions of the spiral tube, in particular the core portion of the wall. The spiral tube 2 also has its outer surface treated in the same manner as the inner surface, whereby its average chromium content is also higher than the average chromium content of other wall portions of the spiral tube (not including the inner surface of the spiral tube).

The electropolishing electrochemically flattens microscopic small irregularities on the inner surface of the spiral tube 2, whereby dirt does not adhere to the inner surface of the spiral tube when recovering thermal energy from, for example, black water. On the other hand, increasing the chromium content on the inner surface increases the corrosion resistance of the inner surface. Increasing the chromium content of the outer surface of the spiral tube prevents calcification of the spiral tube and maintains the thermal conductivity (heat penetration) of the spiral tube at a high level.

As mentioned above, the inspection hatch-manifold-heat exchanger 7, 6, 3 constitutes a single entity which is easy to lift all at once, thus facilitating important maintenance of the interior of the container 1.

Such inspection hatch-manifold-heat exchanger 7, 6, 3 entity is represented in fig. 4, but can also be seen in fig. 1.

In the sectional view of fig. 6, the horizontal angle of the spiral tube 2 is illustrated. Helix 2 of helix tube 2¹(i.e., the threads of the helical tube) has a helix radius R1 outside of the bend t. The radius is the distance from the vertical centerline H of the helix to the centerline of the helix. In contrast, at each horizontal angle (i.e., at bend t), the distance or radius of curvature is R1' again measured as the distance from the vertical centerline H of the spiral pipe 2 to the centerline of the spiral. Helix angle t affects wastewater J at helix 2¹…2⁸And thus affects the heat transfer from the liquid flowing inside the spiral tube 2 to the heat transfer fluid L surrounding the spiral 2.

In the foregoing examples, only a few embodiments of the invention as defined in the claims have been presented, it being obvious to a person skilled in the art that many other possible embodiments of the invention are possible.

List of reference numerals (main assembly)

1 Container

2 spiral pipe

21, 22 Inlet and outlet connections (for spiral pipes)

3 shell and tube heat exchanger

31, 32 inlet and outlet ports (for shell and tube heat exchangers)

4 first heat transfer space

4; 41 Heat transfer fluid inlet connection

4; 42 heat transfer fluid outlet connection

5 second Heat transfer space

6 inspection hatch

61 Top inspection hatch (cover)

7 manifold

8 flange connecting piece

81 spiral heat exchanger

9 waste water inlet conduit

9; 92 waste water outlet conduit

10 (of the container)

11 additional heat transfer space inside the miniature spiral

12 (of the container) holder

Claims

1. A container (1) for recovering thermal energy of wastewater, said container (1) comprising: a shell (10) outwardly defining the container; a continuous spiral pipe (2) for conveying waste water through the vessel in a vertical direction, the spiral pipe (2) communicating with an external vessel waste water inlet conduit (9) via an inlet connection (2; 21) associated with the vessel shell and with an external vessel waste water outlet conduit (9; 92) via an outlet connection (2; 22) associated with the vessel shell; a first heat transfer space (4) surrounding the shell of the spiral pipe (2) and defined by the outer shell of the spiral pipe (2) and by the shell (10) of the vessel (1), and the first heat transfer space (4) communicating with a heat transfer fluid inlet conduit via at least one heat transfer fluid inlet connection (4; 41) associated with the shell (10) of the vessel (1) and communicating with a heat transfer fluid outlet conduit via at least one heat transfer fluid outlet connection (4; 42) associated with the shell (10) of the vessel (1); and a second heat transfer space (5) remaining inside the spiral tube (2) and being defined by the shell of the spiral tube (2), whereby at least a part of the vessel (1) is provided as a pressure vessel,

-the vessel (1) having its shell (10) provided with at least one, preferably two openable inspection hatches (6), at least one inspection hatch (6) securing a manifold (7) and a shell and tube heat exchanger (3), preferably a spiral shell and tube heat exchanger, the shell and tube heat exchanger (3) having its inlet and outlet ends (31, 32) coupled to the manifold (7), the manifold being further provided with means for opening and closing a fluid connection with the shell and tube heat exchanger,

-said waste water pipe, as regards its material, consists of acid-resistant or stainless steel and has at least its inner surface treated so that, by said treatment, said spiral pipe has at least its inner surface adapted to have an average chromium content higher than the average chromium content of the rest of the spiral pipe wall.

2. Container according to claim 1, characterized in that the spiral tube (2) has its inner surface, and possibly also its outer surface, treated with electrolytic polishing for reducing its surface roughness.

3. A container according to claim 1 or 2, characterized in that the spiral tube (2) has its inner surface, and possibly also its outer surface, electrochemically treated to a surface roughness below Ra 120.

4. The vessel according to claim 1, wherein the inspection hatch (6) is coupled to a flange of the vessel by means of bolted joints (16) or the like, and a shell and tube heat exchanger (3) and a manifold (7) are openably coupled to the inspection hatch.

5. The vessel (1) according to claim 1, characterized in that the material thickness of the spiral pipe (2) is selected, with respect to the average cross-sectional diameter of the spiral pipe, on the one hand such that the spiral pipe (2) has a first pressure resistance level, and with respect to the inner diameter of the vessel, on the other hand such that the vessel has a second pressure resistance level, whereby the pressure resistance level of the spiral pipe (2) differs from the pressure resistance level of the vessel (1).

6. Container (1) according to claim 3, characterized in that the average cross-sectional diameter of the spiral pipe (2) is chosen such that the spiral pipe (2) has a pressure resistance corresponding to a pressure classification of 10 to 16 on the one hand, and the material thickness of the shell (10) of the container (1) is chosen such that its pressure resistance corresponds to a pressure rating of-0.5 to 6 on the other hand.

7. Vessel (1) according to claim 1, characterized in that the second heat transfer space (5) left inside the spiral tube (2) has one or more shell and tube heat exchangers (3) located therein, the ratio of the cross-sectional diameter of each shell and tube heat exchanger to the material thickness of the tube being such that the tubular heat exchanger (3) has a third pressure resistance in accordance with pressure classifications 10 to 16.

8. A vessel (1) according to claim 1, characterized in that the shell-and-tube heat exchanger (3) located in the second heat transfer space (5) is made as a separate pressure vessel, from which no substance transfer takes place either onto the tube side of the vessel (1), i.e. into the spiral tube (2), or onto the shell side of the vessel (1).

9. Container (1) according to any one of the preceding claims, characterised in that the container (1) has the inner and outer walls of its shell (10) finished with a treatment that enhances its corrosion and wear resistance.

10. Container (1) according to any one of the preceding claims, characterized in that the container (1) has its shell (10) and/or cover and/or bottom provided with one or more additional connections, preferably flange connections (8), for a heat exchanger for transferring energy into or out of a heat transfer fluid present in the heat transfer space (4, 5, 11).

11. Container (1) according to any of the previous claims, characterized in that said spiral pipe (2) has a continuous interior for adapting the liquid to travel unimpeded in said spiral pipe (2).

12. Container (1) according to any of the preceding claims, characterized in, that the spiral tube (2) has its spiral (2) spiralled¹...2⁸) Designed to have a horizontal angle (t) and/or the spiral (2)¹...2⁸) Has a radius of undulation (R1) starting from the vertical centre line (H) of the spiral tube for varying the flow rate of the liquid flowing inside the spiral tube (2).

13. The container according to any of the preceding claims, characterized in that the flow rate of the liquid or gas present inside the spiral pipe (2) is regulated by waste water flow means outside the container (1).